American alligator description

The largest reptile in North America, the iconic American alligator (Alligator mississippiensis) is considered to be a living fossil, having survived on Earth in the same form for 200 million years (2)(4). The name ‘alligator’ derives from the Spanish ‘el lagarto’ meaning ‘the lizard’, while the species name means ‘of the Mississippi’ (5). Though often confused with various crocodile species, the American alligator can be distinguished by its rounded snout, and by the fact that when the jaws are closed, none of the lower teeth are visible (6). The body is armoured with thick scales, and bears a long, powerful tail, as well as sturdy limbs with webbed toes, which help to propel this species through the water (4)(6). The eyes and snout are positioned on the top of the head, enabling the American alligator to breathe and watch for prey, while the rest of the body is submerged (7). This concealment is further enhanced by the colouration of the body, which is uniform black or olive-brown in the adult, with younger specimens possessing yellow banding across the body and tail (5). The American alligator’s jaws contain between 74 and 80 sharp, conical teeth, and are capable of delivering massive bite forces (2)(5).

Related species

American alligator biology

An opportunistic predator, a fully-grown American alligator is capable of tackling nearly all aquatic and terrestrial prey that it encounters (5). Hatchlings start life feeding on insects and freshwater shrimp, but as they grow they graduate to larger prey, taking fish, frogs and snakes, and eventually small to large mammals (8). While the American alligator is notorious for its potential danger to humans, attacks are very rare, and are usually due to provocation, habituation due to being regularly offered food, or the mistaken identification of humans for smaller prey (5).

The American alligator typically breeds in spring, between late April and early June (8), with male alligators using a variety of behaviours to attract and court females, including deep, powerful roars, slapping the head against the water and complex body postures (5). After mating, the female lays between 25 and 60 eggs in a large, torn-up mound of vegetation and mud situated on a bank or mat of vegetation. The eggs are deposited within a depression in the top of the mound, which is then covered over with more vegetation. This nest not only protects the eggs from flooding, but also aids incubation, due to the heat produced by the rotting vegetable matter (5)(8). While in the nest, the temperature to which the eggs are exposed determines the sex of the hatchlings; hence, due to variations in temperature in different parts of the nest, a mixed-sex litter is usually produced (8). Incubation usually lasts for around 65 days, depending on temperature, after which time the female, which remains in close proximity to the nest to guard it from predators, responds to calls made by the hatchlings and digs them out. Around eight to ten offspring at a time are then carried to the water in the female’s jaws. The juveniles remain close to the mother for around a year, but occasionally up to three years. Despite the maternal protection, the young are regularly preyed upon by raccoons, large fish, birds, and by large, dominant, male American alligators (5).

The American alligator is considered to be a keystone species, which means that through its activities it plays a key part in ensuring a healthy, biodiverse ecosystem. One major contribution to this role is the construction of “alligator holes”, which are depressions dug out by the alligator using its snout and tail, which hold water, providing a refuge during dry periods (5)(6). The holes provide a vital source of water for fish, insects, crustaceans, snakes, turtles, birds, and other animals (4), which further benefits the alligator by providing a convenient source of food (6). In addition, to drought, the American alligator is also capable of surviving at sub-zero temperatures. As temperatures drop, the alligator’s metabolic rate decreases, and it ceases to forage below 20 to 23 degrees Celsius, retreating to an excavated burrow where it survives the winter using stored energy reserves. Amazingly, outside its burrow, this species is also capable of surviving freezing conditions, submerging its body, but keeping its nostrils above the water to breathe, which then become trapped in the surrounding surface ice (5).

American alligator range

The American alligator is found in the south-east of the U.S.A., occurring in the states of Alabama, Arkansas, North and South Carolina, Florida, Georgia, Louisiana, Mississippi, Oklahoma and Texas, as far west as the Mexican border (2)(5).

Species with a similar range

American alligator habitat

The American alligator is typically found in freshwater swamps and marshes, as well as in rivers, lakes and smaller water bodies. While saltwater is usually avoided, a degree of salinity can be tolerated for short periods, and individuals are sometimes found in brackish water around mangrove swamps (5).

American alligator status

American alligator threats

Although the American alligator currently has a large and healthy population, during the 1950s this charismatic species was in danger of extinction (5)(6). Widespread hunting for alligator skin, which is used to make high-quality leather, had resulted in catastrophic population declines, particularly in Louisiana and Florida. Fortunately, prohibition of alligator hunting reversed this trend, and while illegal poaching remained a problem, this too was later addressed through laws controlling movement of alligator hides (5).

Today, the main threats to the American alligator are habitat loss and degradation. Encroachment of human development on unprotected wetland areas is removing suitable habitat for this species. In addition, pollution is also having a detrimental effect, with low reproductive success and deformities exhibited by alligators exposed to high concentrations of contaminants (2).

American alligator conservation

The American alligator’s remarkable recovery is an excellent example of a conservation success story. A law passed in 1967 classified this species as endangered, providing formal recognition of its precarious status. Subsequently, in 1973, the American alligator was listed on the newly passed Endangered Species Act, prohibiting all hunting. As the numbers began to recover, monitoring programs were set-up by State wildlife agencies to ensure a continued population increase. By 1987, the population was considered fully recovered and removed from the endangered species list (4). Despite it’s recovery, the American alligator remains listed on Appendix II of the Convention on International Trade in Endangered Species (CITES), which ensures that trade in products from this species is controlled through the use of permits and quotas (3). It is also still listed by the Fish and Wildlife Service under the Endangered Species Act as “Threatened due to similarity of appearance” The purpose of this regulation is to protect related, “look-alike”, endangered species such as some crocodiles and caimans, which may be hunted illegally, and the products passed off as coming from American alligators (4).

One of the most pressing concerns for the American alligator is the loss and degradation of its habitat. While protected areas provide a refuge for many populations, as a keystone species, the preservation of as much of this species’ habitat as possible is necessary to ensure healthy, biodiverse ecosystems (2)(5).

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